Why is my hair really wavy when I get out of the shower but straight and thick when it dries?

Is it because I tousle my hair when I scrub it with shampoo? I do scrub pretty viciously and for a long time. I think it's straight but my mom said it's curly but I think my hair is straight when it dries. Except there may be a slight wave or two, very minimal waves, if any when it's dry. But it has a lot of volume when it's dry. Right now, it's damp from getting out of the shower 30 minutes ago and it's really wavy, kind of curly but mostly wavy I think. does that make my hair naturally wavy or straight?